A Beer’s Changing Profiles, Copper Questions, and Kräusening For Homebrewers
Q I have brewed a Founders Brewing Co.’s Breakfast Stout clone from the BYO Big Book of Clone Recipes every year when it gets cold outside. It is fantastic and find it gets very close to Founders’ version. I brew the recipe exactly as printed using cocoa nibs and Kona and Sumatran coffees. One thing I have noticed is that the Founders’ beer seems to have a very consistent flavor profile with a nice balance of the chocolate and coffee while the chocolate and coffee flavors in my homebrewed version change dramatically over a period of about three months. In the beginning, the coffee flavor is dominant and it can be difficult to taste any chocolate. After a few weeks the coffee calms down and a milk chocolate flavor starts to appear. After a few more weeks the coffee flavor turns really earthy and the chocolate flavor turns dry and almost bitter. Is there a way to stabilize these flavors?
Shawn Poggemiller
Dubuque, Iowa
A Just reading this question makes me want to stop writing and go find one of these great beers! Describing off-flavors can be difficult, especially in beer styles with a combination of special ingredients like coffee and chocolate, special malts, and alcohol. Whether my hunches are correct about the causes of your specific problems are correct or not, they certainly will not hurt anything when followed.
The first thing that comes to mind is oxidation because oxygen has a way of dulling most fresh flavors in beer, wine, and food. And oxidation has an irritating way of changing the flavor of beer over time, like you are describing in your Founders Breakfast Stout (FBS) clone. When in doubt, consider oxidation! However, obsessing about oxygen can become bothersome and paralyzing at times, but a healthy respect of the negative effects of oxygen on beer flavor stability is a good thing. One of the easiest and most effective practices to ward off oxygen, especially in stronger beers that may spend a longer time in the fermenter, is to rack into a keg. I know the trend these days is one-pot everything, but racking has some real benefits.
Benefit #1 to racking is ditching some yeast. This can certainly be done without racking if your fermenter has a valve on the bottom that allows for purging, but a lot of brewers still ferment in containers without this feature. I’m not sure what you use, but consider racking if you are aging on yeast. What does racking and yeast sediment have to do with beer stability? Well, when yeast is left lying on the bottom of a fermenter, especially beneath higher-alcohol beer, it dies and decays (lyses) over time. And when yeast cells break apart as autolytic enzymes do their thing, these and other enzymes spill into beer. This cocktail of enzymes can lead to enzymatic degradation of beer aroma compounds from esterases, degradation of beer foam from proteolytic enzymes, a general dulling of aroma, and the development of umami flavors (soy, meaty, brothy). Getting yeast sediment away from beer is always a good idea after the heavy lifting of fermentation is over.
Another benefit of racking into a keg is to definitively seal the beer up from the environment. This can also be done in a stainless fermenter, but not all homebrewers have these silver gems. Filling a Corny keg with water, blowing down with carbon dioxide, and racking in through the dip-tube is an easy and effective way of moving beer. Since the Founders clone has coffee grounds added to the fermenter, racking also gets the beer off of the coffee. Sitting on grounds for prolonged durations may lead to issues.
If your beer is bottled, check out your process and make sure you are doing everything you can to minimize oxygen in the package.
If your beer is bottled, check out your process and make sure you are doing everything you can to minimize oxygen in the package. Bottling is a major thing for homebrewers because beer does not foam when filling flat beer into bottles. Many brewers, both commercial and recreational, place way too much faith in the antioxidant property of yeast. Chemical oxidation occurs very rapidly and sleepy yeast are unlikely to absorb oxygen introduced during packaging fast enough to prevent beer oxidation. Founders packages all of their major brands after carbonation and is able to crown/lid on foam. This is a great way of pushing air out of the bottle headspace. If you are capping flat beer, that air in the headspace is 19% oxygen. Adding some fresh yeast at bottling time is one way to address this issue, especially for beers that are being bottled with priming sugar 4+ weeks after brewing. But don’t be tempted to fill bottles with little to no headspace. My preference is to counter-pressure fill and crown on foam, even when doing some secondary fermentation in the bottle. That’s a discussion for another day.
Besides oxidation and prolonged exposure to yeast sediment, another thing that pops to mind is ingredient selection. Although the types of coffee and chocolate are specified in the recipe, no specifics about quality is provided. Quality can be a nebulous term and it’s impossible to have agreed upon quality metrics without some sort of testing methods. Cacao nibs, chocolate, and, especially, roasted coffee all are subject to oxidation. The general advice from coffee roasters about the storage of roasted beans is to use them within about two weeks of roasting for the freshest flavor. Ingredient quality, particularly with non-traditional brewing ingredients, can be a real game changer. Not much more to comment on this without knowing more about your coffee and chocolate sources. The bottom line is that you want fresh ingredients with great taste and aroma profiles.
The last thing that comes to mind is probably a stretch, but water chemistry is certainly an important factor for all beers. Aroma decay is not something associated with water chemistry, but the balance of a beer without a lot of roasted malt and roasted adjuncts can definitely be affected by water.
Years ago, I heard a great story from a practical brewer that was part fable and truth. This brewer proclaimed that the brewery brewed the best, most consistent beer possible, and then the packaging department messed everything up by packaging the brewery’s beer. Not so much a story about throwing the packaging department under the bus, but a story of life and recognizing the finite time we, and our beers, have before succumbing to the steady beat of the metronome. Extending beer freshness is a multibillion-dollar pursuit and there are no silver bullets. Hopefully some of the tips provided here will help you out. In the meantime, drink your beer fresh and brew more when you run out!
Q I am relatively new to homebrewing and recently bought a copper immersion chiller. It works great for wort cooling, but looks really brown after it dries. Is this something I need to clean off before using the next time I brew?
Pierre Vanden Borre
Gatineau, Québec
A Many brewers and cooks love copperware for its heat transfer properties and attractive appearance. One of the downsides, however, to copper is that pretty, honey-like color turns brown over time and requires polishing to restore the shine. And sometimes, the brownish tint turns green. The good news is that brown and greenish-brown copper surfaces are normal and have no negative effects on brewing. Copper, like most metals, is covered with a visible oxide film. In the case of copper, this film is smooth and brown in color. Over time, the brown film on copper may turn green from sulfur in the atmosphere raining down on exterior surfaces such as gutters, cupola roofs, weather vanes, and sculptures.
Let’s talk about cleaning of copper brewing tools. The most common uses of copper for brewing equipment are brewhouse vessels, especially brew kettles, coolships, Baudelot (falling-film) wort coolers, and, in the case of homebrewing, immersion chillers. One commonality of all of these brewing tools is that they are used on the hot side of brewing in contact with wort (as opposed to beer) and the surfaces that do touch wort are visible. Copper is a good fit for these uses because all benefit from copper’s high thermal conductivity and all are exposed to hot or, in the case of Baudelot chillers, hottish wort. The easiest and most effective way to clean copper vessels and coolers is by using a mild cleaning solution, like sodium carbonate, with some gentle scrubbing with a non-abrasive brush, followed by a water rinse. Strong alkaline cleaners, such as sodium or potassium hydroxide, and acidic cleaners can damage copper. Breweries with real copper brewhouse vessels, as opposed to stainless tanks with copper façades, usually use special cleaners with corrosion inhibitors to prevent their beautiful vessels from slowly wearing away.
Without going down a rabbit hole, it is worth noting that here in the states, the U.S. FDA (Food and Drug Administration) restricts the use of copper in commercial food processing to foods with pH > 6.0, with the exception of brewing, where copper is a permitted wort and beer contact surface. This is because copper can be toxic to people and because acidic liquids dissolve copper from the surface of metals. Copper can also oxidize beer, so very little copper equipment is found in breweries after wort cooling.
The topic of toxicity sounds a bit scary, but a survey of commercially available beers in 2017 found beer copper levels below World Health Organization guidelines for drinking water (Journal of Brewing & Distilling, Vol. 7(1), pp. 1-4, March 2017). There is a benefit to having some copper in wort because copper binds sulfur produced in fermentation. In fact, stainless steel brew kettles often contain sacrificial copper parts or strips specifically for the purpose of adding a bit of copper to wort for sulfur binding. But again, once fermentation is complete, brewers do not want beer to contact copper because copper can oxidize beer.
The next time you use your copper wort chiller, thoroughly rinse after use, clean with a mild detergent and a sponge or brush, rinse, dry, and store. And no worries about the patina, as the brown is just copper oxide. The great thing about immersion chillers is that the sanitizing step occurs immediately before use by simply submerging in the wort during the last 5–10 minutes of wort boiling.
Q I’ve been playing around with fermenting under pressure using a spunding valve and now want to start kräusening. Is that something worth messing around with at home? I am not really clear what this method is and what it is supposed to do for my beer. A liter for your thoughts!
Alan Dufresne
College Station, Texas
Kräusening is a lagering method with two main uses. And both are based on the same basic technique of adding some beer in the “high kräusen” stage of fermentation to beer that has undergone primary fermentation. The attenuation level of the beer being kräusened is what divides the two uses. Let’s start with beer that has undergone a normal and relatively rapid primary fermentation and finish this discussion with beer that is either lagging towards the end of the race or is predicted to soon begin to lag.
Some brewers use kräusening as a routine method of lagering where about 8.5 parts of fermented beer is moved into a lagering tank followed by the addition of about 1.5 parts kräusen beer. These two beers can be brewed from the same recipe or a special kräusen beer may be brewed specifically for kräusening. Breweries routinely kräusening face the challenge of having kräusen beer in the right stage of fermentation, the high kräusen or “high crown” stage, to add to the beer being kräusened. The solution to the challenge is proper planning so that actively fermenting beer with about 75% or more of its original wort gravity is available for kräusening. When a brewer kräusens several different beers, a standard kräusen beer makes sense in a production facility.
Scheduling details aside, what’s up with the method? Kräusen beer is added after the attenuated beer is added to the lagering tank because the kräusen beer is heavier than the other beer and will layer on the bottom of the lagering tank. This is especially relevant when a horizontal lager tank is used. The cool and handy part of this process is that the kräusen beer brings with it healthy and vibrant yeast, fermentable sugars, and wort nutrients. Think of this beer as a fresh crew on a construction site coming to relieve the tired folks who have been working for 10 hours and need to rest.
Because the kräusen beer is layered on the bottom of the tank, the release of carbon dioxide and the generation of heat sets up gas and convective currents in the lagering tank. In other words, the tank is mixed by the action of the fresh yeast on fermentables. Some breweries add surface area to the lagering tank in the form of beechwood chips and this surface area serves as a huge site for yeast to do cool stuff to the fermented beer in the tank. More on that in a second. While you have been reading and I have been typing, carbon dioxide has been sneaking out of the lagering tank, so let’s attach a spunding valve and carbonate our beer while this cool stuff is happening.
Because the kräusen beer is layered on the bottom of the tank, the release of carbon dioxide and the generation of heat sets up gas and convective currents in the lagering tank.
The cool stuff is an increase in maturation rate. Diacetyl and acetaldehyde are the two heavy hitters whose concentrations in beer usually dictate the time required for lagering. Many breweries monitor these two aroma-active molecules before deep chilling and filtration. Because active yeast accelerates the biochemical reduction of diacetyl into 2,3 butanediol and acetaldehyde into ethanol, aging times can be cut when yeast absorbs these “green” compounds from beer, biochemically reduces these by moving hydrogen from NADH to acetaldehyde and diacetyl, thereby regenerating NAD+. Although the concentrations of acetaldehyde and diacetyl are indeed lowered (reduced) by this reaction, the term “reduction” refers the movement of hydrogen in these biochemical reactions.
So in effect kräusening speeds up aging! And by the time the beer is fully attenuated by the clean-up crew, it’s also carbonated with hopefully none of the green aromas of young beer. We are talking brewing here, so things don’t always go as planned and the process must be monitored like anything else. The technique is called kräusening, not Prest-O Change-O.
Kräusening is also an extremely powerful arrow in the brewer’s quiver for warding off lagging, high-gravity fermentations or as an emergency tool to deal with the occasional lagging or stuck ferment. Many of us are surely thinking about brewing strong beers for the winter and are checking out the malty malts for doppelbocks. This is a great style to simply plan on kräusening. The benefits are the same as described above, but unlike kräusening a Pilsner or helles fermentation with kräusen beer that is brewed from the same recipe, strong beers, like doppelbock, do not make great kräusen beers because their strength is stressful on yeast. In a commercial brewery with several brews to choose from, a brewer may kräusen as a Plan B emergency and simply grab a bit of normal strength beer from a batch that will not stick out in the beer being jump-started. Drastic times sometimes call for drastic measures, but some lagging ferments should come as no surprise in certain styles. I suggest simply planning on kräusening for bigger beers like doppelbock, barleywines, imperial stouts, etc. Just because kräusening is a lagering method does mean that it cannot be used for ale.
So, let’s finish up with a brief how-to-kräusen summary. In this example, the beer being kräusened is a Mashinator Doppelbock. The minimum wort strength of this fictitious brew, as defined by the conventions of doppelbock naming, is 1.076 (18.5 °Plato) because the suffix “-ator” is used. We’ll revisit that in a moment. OK, here we go:
- The brew day will be normal, except we are going to get a bit clever with our wort strength and volumes. For starters, the target wort strength is going to be bumped to 1.082 (19.65 °Plato) because our beer will contain 85% of the total fermented from 1.082 (19.65 °Plato) wort and 15% of the total from a 1.048 (12 °Plato) wort, for a blended wort strength of 1.076 (18.5 °Plato). The total volume in this example is 6 gallons (23 L) of beer (full-strength wort + kräusen wort).
We also will prep for kräusening by pulling 0.55 gallons (2 L) of 1.082 (19.65 °Plato) wort and diluting to 1.048 (12 °Plato) by adding about 0.35 gallon (1.3 L) of water, then freezing for future use as kräusen beer.
At the end of the brew day, the goal is to start our fermentation with about 5 gallons (19 L) of 1.082 (19.65 °Plato) wort. - For this example, the transfer trigger into lagering will be when our fermentation has dropped to about 1.028 (7 °Plato) because that’s about when fermentation rate can begin to lag. In other words, we want the relief crew to start working before the day shift packs it up for the evening! This is where some educated guesswork is required.
- When the fermentation is down to around 1.034–1.036 (8.5–9.0 °Plato), we are going to take our frozen wort from the freezer, thaw, boil to sterilize, cool, aerate, and pitch with fresh yeast. Whether liquid or dry, pitch based on the volume of kräusen beer. In this example, that’s 0.9 gallon (3.3 L). This mini-fermentation can be conducted in a glass jug or small bucket. After about 48–60 hours, the fermentation should be in the high kräusen stage and ready for use.
- Rack the high-gravity beer into a Corny keg, a handy 5-gallon (19-L) lagering vessel, through the dip tube (the keg’s “Out” connection), then rack the kräusen beer into the keg, again through the dip tube, connect a hose to an “In” fitting, and insert the end of the hose into a container of water. This allows for visual monitoring of the fermentation by observing gas bubbles and also allows time for carbon dioxide to freely escape the lagering tank and flush oxygen from the headspace. After 1–2 days of fermentation, replace the hose with a spunding valve adjusted to the correct pressure for the tank temperature. In this case, assume the lagering tank is at 50 °F (10 °C) and we want to equilibrate at 18 psig (gauge pressure) for about 2.5 volumes of gas. As fermentation builds pressure in the lagering tank, the spunding valve will begin to vent excess gas once the pressure reaches 18 psig.
- That’s it until fermentation is over. Taking samples is only required if you want to. If this beer is for holiday enjoyment, I would leave it at 50 °F (10 °C) for about three weeks, sample at the end of this period to confirm that the show is over, remove the spunding valve, then transfer the keg into a cold spot.
